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Jo Cox, 41, advocated for Britain staying in the EU and also focused on Syria

She was "always friendly, cheerful and kind to friend and foe alike," Nick Clegg says

(CNN)Before she was attacked and killed Thursday, Jo Cox was known for her vocal stances in the Brexit debate and other political flashpoints -- as well as her beloved persona in and out of Britain's Parliament.

"You just can't fault the woman. She was perfect in every single way," fellow Labour Party politician Shabir Pandor said.

Cox, 41, was a staunch supporter of Britain voting to stay in the European Union, a volatile issue that will go to a referendum next week. In a June 10 tweet, Cox advocated her position.

"Immigration is a legitimate concern, but it's not a good reason to leave the EU," she wrote.

As for members of her Labour Party, Cox's death marks an enormous loss.

"It's just unbelievable," Labour Party lawmaker Rushanara Ali said. "I don't think anyone could think this could happen to such a courageous, kind and committed member of Parliament who was killed in the line of duty."

Advocate for many causes

Jo Cox participated in a Parliamentary tug of war contest for charity this month.

Before Cox was elected to Parliament last year, representing Batley and Spen, the mother of two spent a decade with the aid agency Oxfam, her website states.

Her first speech to Parliament last year -- known as a maiden speech -- reflected the love and respect she had for her diverse region, made up of "independent, no-nonsense and proud Yorkshire towns and villages."

"Our communities have been deeply enhanced by immigration, be it of Irish Catholics across the constituency or of Muslims from Gujarat in India or from Pakistan, principally from Kashmir.

"While we celebrate our diversity, what surprises me time and time again as I travel around the constituency is that we are far more united and have far more in common with each other than things that divide us."

Cameron lauded her, saying she had a "great track record of caring about refugees and had taken a big interest in how we can look after Syrian refugees and do the right thing in our world. "

Cox and Conservative MP Andrew Mitchell wrote a column last year in the Guardian called "British forces could help achieve an ethical solution in Syria." She endorsed approaches on the humanitarian, military and diplomatic fronts.

"As two people who have both worked for many years at different ends of the humanitarian aid spectrum -- as an aid worker and as secretary of state for international development -- we agree on one thing: There is nothing ethical about standing to one side when civilians are being murdered and maimed. There was no excuse in Bosnia, nor Rwanda and there isn't now."

Labour Party politics

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Cox dived into Labour Party politics and advocated strong leadership for the movement. She co-wrote a column with Labour Parliament member Neil Coyle in the Guardian about how she regretted nominating Jeremy Corbyn to lead the party.

"We helped put Corbyn on the ballot because we wanted a genuine debate within the Labour Party. We didn't expect to be debating things far from the priorities of most voters: unilateral nuclear disarmament, the Falkland Islands, the monarchy and all the rest. Important issues, perhaps, but not ones that swing elections. Why should we be surprised if people are turning their backs on a party that appears to have stopped talking about the things that are relevant to them?

"Weak leadership, poor judgment and a mistaken sense of priorities have created distraction after distraction and stopped us getting our message across."

She was a frank opponent of the Conservative agenda and its champions.

"Today David Cameron, George Osborne and Boris Johnson are even more determined to allow inequality, unfairness and injustice to prevail while our public services go to the wall. Every time we flounder we just embolden them further," she wrote, referring to top Conservative politicians.

First graduate, mother and wife

A mourner places flowers at Birstall's Market Square in honor of Jo Cox.

Cox was the first person from her family to graduate from university, her biography says.

When she wasn't in Parliament, Cox split her time between two homes: one in Batley and Spen, and one a boat on the River Thames.

Brendan Cox said his slain wife would have wanted two things above all right now:

"One, that our precious children are bathed in love; and two, that we all unite to fight against the hatred that killed her."